Currently, three-dimensional (3D) video images are broadcasted (3D broadcasting). For example, the channel BS 11, which is a Japanese digital satellite broadcasting channel, performs 3D broadcasting by the “side-by-side method” in which a video image for a single screen is transmitted by dividing the image into a left eye video image and a right eye video image. In addition, the “polarization method” and the “active shutter method” are known as typical display methods for 3D video images. The active shutter method is also referred to as the time-division display method, the frame sequential method or the like.
In the case of the polarization method, a receiver for 3D broadcasts includes a film having polarization properties on a display panel, and carries out an interlaced display of left eye video images and right eye video images. A viewer wears polarization glasses and views the display lines for the left eye video images with his/her left eye, and views the display lines for the right eye video images with his/her right eye, thereby enabling stereoscopic perception of video images.
In the case of the active shutter method, the 3D broadcasting receiver alternately displays left eye video images and right eye video images. A viewer wears glasses including a liquid-crystal shutter. The glasses control the liquid-crystal shutter such that the left eye video image enters his/her left eye only and the right eye video image enters his/her right eye only. In this manner, a viewer can perceive video images stereoscopically.
Incidentally, a phenomenon called burn-in may occur on a display panel. Burn-in is a phenomenon in which degradation of light-emitting devices advances due to lighting the light-emitting devices for a long time, leading to a condition in which its light-emitting function is not performed properly. Especially, in the case where a still image or a moving image including a still region is displayed for a long time, such an image may sometimes remain on the display panel like an afterimage due to burn-in.
In this manner, burn-in is caused by degradation of the light-emitting devices, and may occur both with two-dimensional (2D) video images and 3D video images. Some techniques for suppressing burn-in from occurring are currently known.
Japanese Patent Laid-Open No. 2000-338947 discloses a technique for mitigating burn-in by the method so-called “pixel shifting”, which, when an input image does not change for a certain amount of time, changes the display size of the image to shift the display position thereof.
Japanese Patent Laid-Open No. 2004-264366 discloses a technique in which the input format of an image is detected and interpolation is carried out in accordance with the display size. Then, burn-in is mitigated by shifting, by one pixel per prescribed amount of time, the display position of the image in horizontal and vertical directions within a prescribed pixel range, while suppressing visual distractions caused by the shifting of the image.
Japanese Patent Laid-Open Nos. 2000-338947 and 2004-264366 aim at applying a pixel shifting to 2D video images, but do not give consideration to the case that video images include left eye video images and right eye video images. Nevertheless, when processing such as conventional pixel shifting is applied to 3D video images, there is a possibility that the 3D video image is perceived with a different stereoscopic effect from that originally intended by the creator thereof, due to the following reasons.
For example, in the case of the polarization method, if the pixels for the left eye video image are shifted to the positions of the pixels for the right eye video image and, the pixels for the right eye video image are shifted to the positions of the pixels for the left eye video image, the parallax between the right and left eyes is inverted. Also in the case of the active shutter method, the parallax between both video images fluctuates when the shift amount of the pixels for the left eye video image and that for the right eye video image are different from each other, or when the shift timings for the pixels for these video images are different from each other. In the 3D video image, people can perceive video images stereoscopically by providing parallax (binocular parallax) between the left eye video image and the right eye video image. However, as a result of the parallax based on which a video image is designed being changed due to a burn-in control, it is anticipated that the 3D video image becomes blurred, or in a worse case, fails to be perceived as a 3D video image. That is, conventional burn-in mitigation techniques have not given consideration to the issue of burn-in in the 3D video images.